Improvement in speaking-telephones



G. M. PHELPS Speaking-Telephone.

No. 220,209. Patented Sept. 30,1879.

UNITED STATES PATENT OFFICE.

GEoRGE M. PHELPS, on RRooKnYN, NEW YORK.

IMPROVEMENT IN SPEAKING-TELEPHONES.

spcdification forming part of Letters Patent No. 220.209, datedSeptember 30, 1879; application filed December 21, 1877.

To all whom it may concern:

Be it known that I, GEoRGE M. PHELPS, of Brooklyn, in the county ofKings and State of New York, have invented certain new and usefulImprovements in Telephonic Instruments, which improvements are fully setforth in the following specification, reference being had to theaccompanying drawings.

My invention relates to a certain class of instruments technically knownas speakingtelephones, which are especially adapted to the transmissionand reproduction at a distance of sonorous waves or vibrations of everydescription by means of electrical impulses or waves traversing acircuit of conductors.

My improvement consists in constructing the yocalizing-chambercontaining the vibrating diaphragm with its rear wall parallel, ornearly so, to the surface of the diaphragm, and with as little spacebetween them as possible, whereby the confusion and indistinctness ofthe sounds produced by the vibrations set up in the confined body ofairin the rear of the diaphragm are altogether avoided.

In the accompanying drawings, Figure 1 is a longitudinal section of atelephonic instru- .ment embodying my improvements, and Fig.

2 is a transverse section taken in the plane of the line at d in Fig. 1.

The instrument shown in the drawings is adapted to be used either forthe transmission or the reception of articulate or other sounds,

and in its general construction and arrangement does not difiermaterially from those heretoforeused for the same purpose.

The body of the instrument A may be composed of wood, vulcanized rubber,or other convenient and suitable material. It is tubular in form, and'isprovided with a solid head or flange, a, as shown in the figure at oneend, upon which is screwed a cap, 13. The latter is provided with aconical or funnel-shaped aperture, b, passing through it' from theoutside and opening into a shallow circular vocaliziug-chamber formed inthe face of the cap which contains the vibrating plate or diaphragm D.This diaphragm is simply a thin elastic disk, preferably of iron orsteel. It is placed with its center in close proximity to the extremityof the core of the helix E, which core is attached to or may form aconstituent part of the permanent magnet F. The distance between the endof the core of the helix E and the diaphragm D is adjustable by means ofthe nut g, which may be turned upon the screw f by means of a suitablekey.

The screw f being fixed in the end of the permanent magnet F, theturning of the nut g in one direction or the other serves to effect thenecessary adjustment, while the pressure of the coiled spring 70 takesup any lost motion which may arise from looseness of the movable parts.I

The wires 6 e, which form the extremities of the helix E, terminate inbinding-screws h h, for the attachment of the conducting-wires of thetelegraph-line.

Between the edge of the diaphragm and the body of the instrument areinterposed dampers d d, which should be composed of some suitablesemi-elastic material. I have found a thick porous quality of paper togive very excellent results in practice. These dampers are placed one oneach side of the diaphragm, and are preferably made in the form of aflat ring, as shown at din Fig. 2. By the addition of these dampers theclearness of articulation is materially increased.

The walls of the vocalizing-chamber, which contains the vibratingdiaphragm D, are made parallel to the surfaces of the diaphragm, or asnearly so as possible.

The space between the rear surface of the diaphragm D and the wall ofthe vocalizingchamber, which faces it, is only just sufficient to admitof its free vibration. This method of construction also greatly improvesthe articulation of the instrument, as in telephones heretoforeconstructed the presence in the rear of the diaphragm of a body ofconfined air of sufficient extent to be capable of being thrown intovibrations which are reflected back against the diaphragm tends torender the sounds confused and indistinct. This interference is entirelyavoided by the arrangement which I have described, as the body of air istoo small to admit of this action taking thereto, substantially as andfor the purpose place to an injurious extent. specified.

I claim as my inventiou- In witness whereof I have hereunto set my In atelephonic instrument, a diaphragm or hand this 17th day of December, A.D. 1877. vibrating plate, in combination with a vocaliziug-chamber, therear wall of which has its Witnesses: surface parallel, or nearly so, tothe surface of the said plate, and closely approximating G. M. PHELPS.

GERRITT SMITH, G. A. HAMILTON.

